Untreated wastewater of municipal or industrial origin has a severe, negative impact on the environment. This is especially true for the wastewater generated in the food processing industries and in sanitary landfills (landfill leachate). In that sense, the commercial opportunities for decentralized wastewater treatment plants, also known as package plants, are huge. As environmental regulations in industrialized countries become stricter, the installation of obsolete decentralized systems (aeration ponds, septic tanks, trickling filters) will be either banned or severely restricted. Indeed, certificates of approval for many of those methods are already increasingly difficult to obtain. These obsolete technologies are being replaced by compact, efficient and economically effective ones.
The treatment of wastewater from landfills or from wineries and fruit-processing plants is far more complex than the treatment of typical domestic wastewater. Wineries and other agricultural and food processing plants generate wastewater that due to its composition and high organic load, seasonal variability and acid and malodorous nature represent a serious environmental problem. Along with the wastewater, sludge is produced both during wine production and wastewater treatment and is collected at the bottom of tanks, holding ponds, and wastewater treatment units. A winery generates 40 to 60 L of wastewater for each case of wine produced. The nature of the wastewater is extremely variable in quality and quantity throughout the year, as it depends on the soil, the type of grapes, and the winery operation underway at any particular time, and the location where the sample is taken. Thus, although there is not “typical” winery wastewater, the following ranges can serve as useful guidelines for the numerical values of its constituents: pH [2.5-11], BOD5 [700-27,000], COD [500-35,000], TSS [400-6,350], Total Nitrogen [20-350], DO [0.5-3.8], and Total Phosphorous [2-60]. The above seven constituents of winery wastewater are of special interest to regulators due to the high levels found in winery wastewater relative to domestic wastewater. As prime vineyard land becomes increasingly expensive, using less space to deal with the treatment of wastewater is becoming a technical and economic challenge. In addition, increasing both wine production and surcharges for treating their wastewater in municipal plants are inducing wineries to treat their wastewater on-site. Unfortunately, most of the wastewater treatment technologies presently available are either very inefficient, very land intensive or both. Aerated lagoons or ponds are acceptable solutions when both, land is abundant and cheap, and concerns about odours and underground seepage are not environmental issues. In addition, aerated lagoons are hard to control. Indeed, low temperatures and rains can have a very negative effect on the performance of the pond. The hydraulic residence time of the wastewater in ponds is measured in months and foul odours and aesthetically unpleasant sights are common. On the positive side ponds require little supervision. However, the use of ponds is being rapidly restricted and the concession of permits by regulatory agencies is becoming increasingly difficult.
Another rudimentary technology very much used by small wineries, rural business and households is the septic tank. On the positive side is its moderate initial capital cost. On the negative side is the fact that this treatment method is paradoxically recognized as a major water polluter. Its removal efficiency is exceedingly low and its performance is unpredictable as it depends on the nature and topography of the land where it is installed. Furthermore, the owner's sense of responsibility to avoid both the use of certain domestic chemicals and pumping the tank according to certain schedules make the septic tank a primitive and unreliable method. The land requirement relative to its treatment capacity is very high and its use is associated to unpleasant odours and the pollution of aquifers. Septic tanks are a source of widespread concern.
Leachate from municipal landfills and septage from septic tanks, often hauled by trucks for treatment in municipal plants, are even more problematic as sources of wastewater. These types of wastewater contain many unpredictable chemical pollutants including toxic metals, high ammonia concentrations, refractory, chlorinated compounds, domestic chemicals etc. so that conventional biological treatments can be severely affected by toxic shocks or surges leading to operational malfunction of the plant. Municipal wastewater consists of a number of wastewater streams including domestic, industrial, landfill leachate, and septage wastewaters. Thus, although, one cannot talk of a typical municipal wastewater, the following pollutant ranges, obtained from the Municipal Wastewater Treatment EDAR Toledo in Spain, represent well municipal wastewater containing landfill leachate and septage: BOD5 [400-1300] mg/L, COD [ 650-2200] mg/L, TSS [ 300-1700] mg/L, Ammonia [ 50-110] mg/L. In addition, many undetermined pollutants form part of this kind of wastewater. The performances of the Active Biological Contactor (ABC) with the aforementioned wastewaters are presented in this document.